Question
Evaluate the following:
$\cot^{-1}\Big\{\cot\Big(\frac{21\pi}{4}\Big)\Big\}$

Answer

We have
$\cot^{-1}\Big\{\cot\Big(\frac{21\pi}{4}\Big)\Big\}$
$=\cot^{-1}\Big[\cot\Big(5\pi+\frac{\pi}{4}\Big)\Big]$
$=\cot^{-1}\Big(\cot\frac{\pi}{4}\Big)$
$=\frac{\pi}{4}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

If $\vec{\text{a}}$ is a vector and m is a scalar such that m $\vec{\text{a}}=\vec0$, then what are the alternatives for m and $\vec{\text{a}}$?
By using the properties of definite integrals, evaluate the integral $\int\limits_0^{2\pi } {{{\cos }^5}x} dx$
Fatima and John appear in an interview for two vacancies for the same post. The probability of Fatima's selection is $\frac{1}{7}$ and that of John's selection is $\frac{1}{5}$. What is the probability that,
Only one of them will be selected?
For what vaiue of $\lambda$ are the vectors $\vec{\text{a}}=2\hat{\text{i}}+\lambda\hat{\text{j}}+\hat{\text{k}}$ and $\vec{\text{b}}=\hat{\text{i}}-2\hat{\text{j}}+3\hat{\text{k}}$ perpendicular to each other?
If A = {3, 5, 7} and B = {2, 4, 9} and R is a relation given by "is less than", write R as a set ordered pairs.
If sinx is an integrating factor of the differential equation $\frac{\text{dy}}{\text{dx}}+\text{Py}=\text{Q}$ than write the value of P.
If $\vec{\text{r}}=\text{x}\hat{\text{i}}+\text{y}\hat{\text{j}}+\text{z}\hat{\text{k}},$ then write the value of $\big|\vec{\text{r}}\times\hat{\text{i}}\big|^2.$
If $B$ is a skew-symmetric matrix, write whether the matrix $AB\ A^T$ is symmetric or skew-symmetric.
Two cards are drawn at random and without replacement from a pack of 52 playing cards. Find the probability that both the cards are black.
Express matrix as the sum of a symmetric and a skew-symmetric matrix:$\left[\begin{array}{rr} {3} & {5} \\ {1} & {-1} \end{array}\right]$